Stoker control apparatus



c. HOTCHKISS STOKER CONTROL APPARATUS Filed March 17, 1941 s Shedts-Sheet 1 I I I I I I l I I I I I I l I ATTORNEY.

Oct. 2, 194.5. 0. HOTCHKl SS 2,385,311

STOKER conmoz. APPARATUS Filed March 17, 1941 s Sheets-Sheet 2 W @wzm Patented OchZ, 1945".

UNITED STATE s PATENT OFFICE STOKER CONTROL APPARATUS I Cliflord Hotchklss, Milwaukee, Wis., assignor to Perfex Corporation, Milwaukee, Win, a corporation of Wisconsin Application March 11, 1941, Serial No. 383,654

26 Claims.

provide a device which acts in response to extinguishment of the fire to operate the igniier device and either shut down the stoker entirely or to discontinue the air feed onfuel feed for a period of time and then restart the stoker, air feed orfuel feed. This stoppage of the feeding of air while the igniter operates causes the heatfrom the igniter to remain in the coal, thus permitting the coal to be heated quickly to ignition temperature with a relatively small energy inputto the igniter. The stoppage of the fuel feed limits the amount of fuel heated by the igniter and thus also increases its effectiveness. I

A further object of the invention. is to provide an igniter control system which places the igniter into operation only when the fire is actually or substantially out, and which then intermittently stops and starts the stoker or air feeding mechanism in an effort to establish combustion.

Another object is the provision of an igniter control system which causes operation of the igniter and intermittent stopping and starting oftheairfeedtothe'flrewhentheflreisout,

thus providing a series of attempts to kindle the fire, and which places the stoker out of operation if this series of attempts fails to cause rekindling.

A further object of the invention is in the provision of an igniter control system for stokers which prevents operation of the .stoker should the igniter become inoperative.

Another object is the provision of an igniter control system which maintains the igniter continuously in operation when the fire is out, and

is made to the following description and the accompanying drawings in which:

Figl 1, illustrates diagrammatically one formof the invention; Fig. 2 is a diagrammatic illustration of a sec ond form of the invention; and in which Fig. 3 shows still another form the invention may take.

Fig. 4 shows one condition of operation ofjthe stack control unit of the form in Fig.;3. h

Referring to Fig. 1, reference character I indicates' a boiler or furnace of any desired construction which is provided with the usual smoke pipe 2 for directing products of combustion to a chimney I. This boiler or furnace may be connected with piping or ducts forming a heat distribution system for heating a space. The furnace l-is provided with a stoker mechanism generally indicated as I. This stoker may be f desired construction and is illustrated as having usual hopper I. The conveyer tube I contains a which intermittently stops'and starts the feeding of air. 1 e

A further object is to provide an improved safety controlsystem which permits operation of the stoker for a period of time without combustion, but which provides a safety shutdown in the event that combustion is not eventually obtained.

Other objects of the invention consist in the provision of novel combinations and sub-combinations of control apparatus and will become apparent from the following description and appended claims.

For a full disclosure of the invention reference feed screw 8 of, usual construction which serves to convey fuel from the hopper to the retort, this feed screw ll being driven by an electric motor I through suitable transmission means not shown. The retort S is surrounded bythe usual wind box II, this wind box being, connected to an air inlet duct ll into which airis forced 30 by a fan fan being preferably driven by the motor 9. The Y diagrammatically indicated at If, this side walls of the retort are provided with the usual tuyeres It for permitting entry of air from the wind box ll into the fuel bed within the retort. The stoker l is provided with a suitable device, Preferably this igniter consists of a coiled electric heating element I! located at the inlet to theretort 6. This resistance element is preferably of the tube type, for example I "Calrod." This resistance elementmay be given considerable protection by locating it in a recess within the side wall of the retort as shown.

- 'lhestokermotor l andtheigniter llare controlledby' means of a relay unit II, a stack unit thermostat II which may be located in a space heater by the'furnace l. The relay unit I includes a motor control relay generally indicated as II. This relay is ditically illustrated as comprising -a pull-in 0011 I. which operatu through a-suitable armature a switch arm 2| cooperating with a contact 22. when the coil II is energized the switch arm Ills brought into engagement with contact 2:; and when this c'oll so isdcenergiscdtheswitch arm a retort 5 connected by a conveyer tube 6 to the II and a heat demand responsive means such as n: covering for sage the left hand end of clockwise direction 4| remains in the tact under the action of gravity or springs not shown. The relay unit II also includes a transformer 28 having a line voltage primary 24 and a low voltage secondary 26. The relay unit It also includes an igniter control means indicated generally as 28. This device, while it may take various forms. is preferably a timing device having a bimetal element 21 which is subjected to the influence of an electric heater 28. This bimetal element 21 actuates a movable contact adapted to engage a fixed contact 28. Preferably this timin device is arranged so that when the bimetal element 21 i cold the contacts are disengaged as shown. when the heater 28 is energized, however, the bimetal element gradually increases in temperature and flnally moves downwardly with snap action to cause engagement of the contacts. This device may be designed so as to require approximately a ten minute period after'heater 28 is energized before the contacts engage. Also thisdevice may be designed so as I v to require a cooling period of approximately ten minutes before the contacts open with snap action after deenergization of heater 28. Any suitable form of snap acting mechanism may be incorporated in timer 28. this being illustrated as comprising a u-shaped permanent magnet.

Referring to the stack control II, this device includes a lockout switch comprising a lever to which is pivoted at If and which is provided with a manual reset handle 82 at its other end. This lever carries a contact which is adapted to engage a stationary contact 88. Lever 34 is also provided with an insulating latch member 84 which is formed to provide a pair of retaining surfaces ii and 88. The surface .88 cooperates with a bimetal element 81 which is supported at its lower end and subiected to the influence of an electric heater 88. The bimetal element 81 and its associated heater 88 form a timing device for terminating operation of the stoker in the event of failure of the ment is preferably provided with a heat insulata p rpose which will appear as this description proceeds. When the bimetal ele-' ment 87 engages the surface 88 the lookout switch lever is held in its upward position for causing the lookout switch to be closed. when the bimetal fire to ignite. This bimetal ele- 42 when this arm is in its "cold position. Preferably the stack element 48 and the stack arm constitute a calibrated combustion responsive instrument. the stack arm 4| being adjusted by any suitable adjusting means (not shown) so as to en age the retaining surface 88 and open the stack switch when the stack temperature is above approximately 125 F., the stack arm 4| disengaging the surface 28 and causing closure of the stack switch when the stack temperature is below this value. This temperature value is of course merely illustrative and the setting of theinstrument may be varied considerably in either direction for different installations and fuels. In some types of installations or for burning some types of fuels it may be desirable to employ a slip friction mechanism between the thermal'element 40 and the stack arm 4|.so asto cause the stackarm to be moved between its hot and cold positions simply upon reversals in stack temperature without regard to the-actual temperature values.

Operation of Figure 1 tact 22. At this time the heater 28 of the timing device 28 is deenergized, which causes the bimetal element to assume the cold position wherein the contacts are disengaged. Also the stack temperature is relativel low as indicated by the stack arm 4i of the stack control being in the cold position wherein. it is disengaged from the retaining surface 88 andcauses closure of the stackswitch. The bimetal element ILfor the lookout switch is cold whereby it engages the retaining surface 88 for maintaining the lookout switch in the closed position. The transformer primary is energized at this time by a circuit extending from line wire 45, wire 48, primary 24,

wire 41, igniter ii, wire 48 and wire 49 to the I lockout switch 80-. wires 82 and 58, thermoelement 81 heats up it warps to the left. and after a substantial period of time disengages surface 88 thus permitting the lever 88 to fall and open the lookout contacts. Upon cooling metal element 81. this element will merely onthe latch member 84 and cannot reclose the lockout switch. In order for this switch to close it isnecessary that'the manual reset handle 82 be lifted. The stack control unit .il also includes a thermostatic element 48 which is located in the smoke pipe 2 and which is adapted to rotate a stack arm 4| in a counter- 7 upon rise in stack temperature. The stack arm 41 is adapted to cooperate with the retainingilirface' 88 when the stack temperature is above a value indicating the presence of-combustion. Thus when combustion is present the stack arm 4| engages the retaining surface 88 and holds the lookout switch closed independently of the bimetal element 81. When combustion is not present, however, the stack arm position shown where it permits dropping of the switch lever 88 when the retaining surface 88 is disengaged by the bimetal element 81. The stack arm 4i also actuates-a stack switch illustrated as a -movablcontact of the bistat i8, wires 84 and 88, pull-in coil 20 and wire 88 to secondary 25. Energization of pull-in coil 28 causes the switch arm 2i to engage contact '22 which establishes an energizing circuit for the stoker motor-8 as follows: from line wire 45,

wire 46, contact 22. switch arm 2i. wire 88, a

high limit temperature or pressure responsive control 88, wire Si, wire 82, motor 8 and wires 48:: and 48 to line wire 88. Simultaneously a parallel circuit is established from wire 8| through wire 68, heater 28, wire. 84, staek'switch 42-, heater 88 and wires 88 and 48 to line wire 58. Thus upon call for heat by the thermostat 18 the stoker motor 8 is placed into operation and the heaters 28 .and 88 are energized.

Due to the heaters 28 and 38 being energized. the bimetal element 21 tends to move downwardly and the bimetal element 21 begins moving very slowly to the left. If a fire is present in the stoker the stack temperature will rise in a short time above E, thus causing the stack switch to open and also causing the stack arm to engage the retaining surface 88. me to the opening of the stack switch the heaters 28 and 88 will be deenerglzed and consequently no further heating of the bimetal elements 21 and 81 will'take place.- Thus under normal conditions when a fire is present in the stoker the igniter igniter I! as follows: line wire 45, wire 46, bi-

metal element 21, contact 29. wire 68, wire 41, igniter l5 and wires 48 and 49 to line wire 50. Thus the igniter I5 will be energized. It will be noted that the contacts of the timing device 26 are in shunt relationship with the transformer primary 24. Consequently when the contacts of the timing device close for energizing the igniter, the primary 2| is completely shunted out so that no current passes therethrough. This deenergizes the relay I 9 which in turn deenergizes the stoker motor 9 and the heaters 28 and 38. Due to the motor 9 being stopped no air is forced around or into the retort and consequently the heat from the igniter I5 is not carried away from the retort as would be the case if motor 9 continued to operate. This permits the coal adjacent the igniter to be heated in a relativel short time to ignition temperature with a relatively small energy input to the heater. Also. due to the fuel feed being discontinued, the fuel remains stationary 50' that the fuel adjacent the igniter remains in such position until the stoker is restarted, thus providing maximum effectiveness of the igniter. Due to the heater 28 now being deenergized, the bimetal element 21 will cool and after a timed period, such as ten 7 minutes, will cause its contacts to open with snap action. This will deenergize the igniter'lS. It will also break tl-e shunt circuit around the transformer primary 24 and consequently the transformer will again be energized which causes reenergization of .the relay I9. This causes operation of the stoker motor 9 and also energization of the heaters 28 and 38. Air will now be supplied to the fuel bed along with fresh fuel and this air incontacting the portion of the fuel bed previously heated to ignition temperature. will cause the fire to burn. Consequently the temperature of the stack willsoon rise to the value at which the stack arm II is moved to its hot position, the stack switch being then opened for deenergizing heaters 28 and II and v the stack arm also engaging the retaining surface 3! to insure maintenance of the lockout switch in its closed pos tion. j

In the event thatiihis first attemptto estabmanner the igniter will remain out of operation and the sicker will remain in continuous operation. Howeven'if this first ignition cycle or attempt fails, the control system will make a number of successive cycles or attempts to kindle the As pointed out previously, the bimetal element 31 is provided with an insulating housing. This causes it to dissipate heat at a rate considerably slower than the bimetal element 21. Thus while the igniter is in operation and the heaters 28 and 38 deenergized, the bimetal element 31 will cool only slightly. Consequently on each successive kindling attempt or cycle the bimetal element 31 will move a little further to the left. After a predetermined number of kindling cycles without obtaining combustion, the element 31 will disengage the retaining surface 35. Due to the stack arm ll being in its cold position at this time the lockout lever 30 will drop, thus causing opening of the lockout switch and deenergization of relay is. This will shut the system down until the manual reset handle 32 is actuated. Itwill be noted that if at any time combustion is estab-' lished, the stack arm 4| is positioned for maintaining the lookout switch closed independently of the bimetal element 11. This arrangement insures against any false lockout as might otherwise occur if combustion is not established until the bimetal :1 is about to disengage the retaining surface '35.

In some systems it may be desirable to employ an interval timer for hold fire purposes, This interval timer is illustrated diagrammatically at 10, including a cam 1| driven by a clock motor not shown, this calm actuating a pair of'contacts 12 and 13 which are connected in shunt with the thermostat 18. These contacts may be arranged to close for a'short interval every half hour or hour so ;as normally to maintain the fire alive. If desired this interval timer may be omitted,

thus allowing the fire to go out whenever the demand for heat is not sufficient to maintainit alive, the kindling device then serving to rekindle the fire whenever necessary.

Figure 2 disclosed in Fig. 2. In this figure the relay unit lish'a fire fails, the heaters "and a will .re-

main energized due to the stack switch remaining closed. Consequently after the timed period of approximately ten minutes the contacts of.

the timer 2' will again close for reenergizing the igniter I! and deenergizing thestoker motor I. At this time the heaters 28 and 32 will once more be deenergized for permitting the bimetal element 21 to cool. After the timed period of anproximately ten minutes the contacts of the timer 2 will reopen for deenergizing the igniter I! and restarting themotor s. Thus it will be apparent that when the fire is out the control system of the present invention will place the stoker, or the air feeding mechanism therefor, out, of operation andenergize the igniter and after a timed period will restart the stoker. In the event that combustion isestablished in this 1' with the II is identical with the unit Ii of P18.

this device exception of the timing device I26. In

the bimetal element I21 instead of actuating a single'switch, actuates a pair of switches l21a and l2s, these switches being electrically insulated. from each other. These switches are arranged to be closed when the bimetal elementm is in its lower or cold position. when the element I21 is heated by the action of the heater I22 itwarps upwardly, causing the switches l21s and 12! to be opened with snap action. To obtain snap action in the opening'and closing of the switches any suitable form of snap action mechatrated as consisting of a permanent magnet l21b cooperatins with a suitable armature secured to the bimetal element I21.

The stack control unit 1 may be of the same nism may be employed. In the drawings this snap action mechanism is diagrammatically illuscalling for heat and consequently the coil I20 of relay II! is deenergiaed. Also the stack temperature is relativelylow which causes the stack element I40 to position the stack arm I in its cold position wherein it causes closure of the stack switch I42.

Upon call for heat by the room thermostat III the coil I20 of relay II will be energized as follows: from transformer secondary I 25, wire III, lockout switch "Ii-I00, wires I 02 and I I0, thermostat 0, wires I04 and IN, relay coil I20 and wire I06 to secondary I20. This energlzation of coil I20 causes switch arm l2I to engage contact I".- This establishes an energizing circuit fOr' the stoker motor I00 as follows: from line wire I40, wire I40, contact I22, switch arm I2I, wire litlimit control I00, wires "I and IOIa, timer switch I20, bimetal element I21, wire I02, motor I00 and wires I40a and I40 to line wire III. The closure oi the contacts or relay III also energizes through the fuel bed to. thereby ignite the same. 1

. the'iguiter III and the heaters I20 andl00 out 1 the igniter III, the heater I20 and the heater I00. The energizing circuits for the igniter and the two heaters-extend through the stack switch I42 whichis connectedby wire-I00 to th'e-wire a I 0I which isenergiaedthrough relay 0 espreviously pointed out. The energizing circuit for the ignlter lll'extends from the stack switch I42 through stack arm.I4I,' wires la and I41, igniter H0 and wires I and Ill to line wire I00. The energizing circuit for the lockout heater assa'su ture by the heater I20'suificiently to cause opening of the switches H111 and I20. Opening of the switch I20 will break the energizing circuit for the stoker motor I00 and thus place this motor out of operation. Opening of the switch I2'Ia will deenergize the heater I 20 and thus per mit the bimetal element I21 to begin cooling. After a suitable period such as ten minutes the bimetal element I21 will be cooled sufiiciently to cause reclosure oi the switches I21a and I29.

This will reenergize the stoker motor I00 and the heater I20 and thus begin a new cycle. It will be noted that during the-period in which the timer I20 places the stoker out oi operation the igniter III continues to operate. This i niter thus heats the coal adjacent to it to ignition temperature. this action being aided by the fact that the stoker I04 is out of operation so that no air is passing through or around the. retort which would carry away the heat from the igniter. After the timer switch contacts recycle the stoker is replaced into operation thus forcing air If the fuel bed ignites properly the stack temperature will rise. thus causing the stack thermostat I40 to open stack switch I42 thus placing of operation. I! this attempt to kindle the fire is unsuccessful the" stack switch I42 will remain closed and the timer I20 will go through another heating and cooling cycle in a second attempt to kindle the fire. This action will continue until the lookout bimetal element I01 warps sufiiciently to the left to disenglge-the -lltch member I04.

Due to the stack arm I4I :being .out'ot; contact with this latch member at this'time the lever "I00 will drop thus opening the lookout. switch I00 extends from the stack arm I through heater I00 and wires I00 and I40 to line wire I40. The energizing circuit for heater I20 extends from the stack arm I through wires I41a and I04, switch I2'Ia, heater I20 and wires "to and I40 to line wire I00. From the description thus far, it will be seen that upon call for heat by the room thermostat IIO the relay H0 is energized which simultaneously energizes the stoker motor,

the igniter. the timer heater I20 and the lockout heater -I00. If the fire is burning the stack temperature will quickly rise to the setting or the stack thermostatic device, thus causing the stack I switch, I42 to be opened with snap action. This will deenergize the igniter III and will also deenergi'ze the heaters I20 and I00. The stoker will then continue to operate until either the thermostat H0 is satisfied .or the furnace temperature or pressure rises to the setting of the limit control I00. If the stoker is operated at fairly irequent intervals the fire will not go out and in tact the stack temperature will remain above the usual setting of the stack thermostatic device,

' thus causing the stack switch I42 to'remain open.

Under these circumstances it will be apparent that the igniter II! will not be operated and the heaters I20 and I00 will not be energized when the stoker starts.

In the event that the fire is out, the stack switch I42 will remain closed thus causing the igniter III to remain energized and also causin 1 the heaters I20 and I00 to .remain energized.

After a period of approximately ten minutes the bimetal element I21 will be raised in temperaand shutting the stoker down until the handle I02 is manually reset.

Figure 3 In Fig. 3 a difi'erent type of circuit is illustrated in which separate low voltage controlled relays are employed for controlling the stoker motor and ig'nlter. In this figure the relay control unit 2l6 may include a transformer 220, a motor control relay 2", a timer 220. an igniter control relay 240 and an interval timer 210. The igniter control relay 240 may be the same asthe relay 2l0 and includes a coil 242, a switch arm 240, and a contact 244. The timer 220 in this case includes a bimetal element 221 which is subiected to the influence of a heater 220. This bimetal element may carry a, pair'ot contacts which cooperate with fixed contacts 221a and 220 and. may be provided with any suitable snap action mechanism (not shown). When the element 221 is cold the movable contacts engage the fixed contacts as shown. However when the heater 220 is energized for a predetermined time the bimetal element 221 is heated sumciently to cause downward movement for disengaging the contacts.

The control unit 2I0 is shown as being controlled by a room thermostat 2I0 oi. the usual construction including abimetal actuated switch 2I0a and an anticipating heater 2I0b.

The stack control unit 2i! includes a lookout switch of the same construction as in Figs, 1 and 2. In this case, however, the bimetal element 201 is arranged so as to deenergize the heater 200 when this element becomes heated, the element 201 then remaining in its hot position by means oi a latch which is controlled by the stack thermostatic element 240. In this device a latch member 240 is pivoted atits right hand end, the

left hand end of this latch member abutting the bimetal element 231 and resting upon a latch member 245 which is secured to element'231.

out switch. The stack arm 2 which is operated by the stack thermostatic element 245 carries an actuating member 241 which is adapted to engage an inclined surface 248 of the latch member 245. Upon fall in stack temperature this actu-' ating member 241 moves clockwise with the stack arm 24! and by engagement with the inclined 1 surface 245 causes upward movement of the latch member 245 for resetting it in the position shown. The latch member245 also actuates a switch for the heater 235, this switch being diagrammati cally illustrated as comprising a movable contact 255 mounted on the latch member and which cooperates with a fixed contact l. When the latch member 245 is in the position shown in Fig. 3 the heater switch is closed as illustrated. However, when the bimetal element 231 warps sufliciently to the left to release the latch member 245 it drops to the position shown in Fig. 4 in which the switch is open. The stack arm 2 in addition to controlling the lockout switch as above described also actuates a pair of switches. These switches are diagrammatically illustrated as comprising a pair of contacts mounted on the stack arm 2, one of which cooperates with a fixed contact 253, the other contact cooperating with a fixed contact 254. When the stack arm 24! is in the cold position as shown in Fig. 3 the switch, including the fixed contact 253, is closed while the switch including contact 254 is open. When the stack arm moves to its hot position as shown in Fig. 4 the first mentioned switch is opened and the other switch closed.

With the parts in the positions shown the room thermostat 2 I5 is not calling for heat and the relays-2l5 and 245 are deenergized which cause the motor 255 and the igniter 2l5 to be out of operation. Also the flre is relatively low or out as indicated by the stack arm 2 being in the cold position. The transformer 223, it will be noted, has its primary 224 continuously connected across the line wires 25! and 252. Upon call for heat by the room thermostat 2l5 the motor relay 2l5 will be energized as follows: I from secondary 225,

wire 253, wire 254, heater 2l5b, bimetal element 215a, wire 255, wire'255, lock-out switch 233-235,

wire 251, stationary contact 2214, bimetal element 221, stationary contact 225, relay coil 225 and wire 255 to secondary 225. Energization of the relay 15 will establish a circuit for the stoker motor 255 as follows': from wire 2", wire 255, contact 222, switch arm 22!, wire 2", limit control 255, wire 212, motor 255, and wire 213 to line wire 252. Closure of the contacts of thermostat 2l5 will simultaneously energize the igniter relay 245 as follows: from secondary 225, wires 253 and m, thermostat, wires m and 200.1001:- out switch 233-235, wires 251 and 2-14, relay coil 242, wire 215, fixed contact 253, stack arm 24! and wires 215 and 255 to secondary 225. Energization of relay 245 will establish a circuit for the igniter 2l5 as follows: from line wire 25l,

wire 255, contact 244, switch arm 243, wire 215, igniter 2l5 and wires 215 and 213 to line wire 252. Closure of the contacts of thermostat 2l5 will also cause energization of the heaters 225 and 235. The energizing circuit for the heater metal element 221, heater- 225, wire as, wire as, stationary contact 253, stack arm 24!, and wires 215 and 255 to secondary 225. The energizing circuit for the heater 235 extends from lock-out switch arm 235, wire 25l, stationary contact 251,

movable contact 255, wire 252, heater 235 and wires 253, 215 and 255 to secondary 225.

From the foregoing it will be apparent that upon call for heat by the thermostat 2 I 5 the motor control relay 2 I 5 and the igniter control relay 245 are energized simultaneously for thereby placing the stoker and igniter into operation. It will also be apparent that the circuit for the motor control relay 215 includes the timer 225 while the circuit for the igniter control relay 245 is independent of this timer but is controlled by the stack switch of the stack control unit 2". It will also be apparent that when the stoker motor and igniter are placed into operation the heaters 225 and235 are energized, the heater 225 being controlled by the timer and the heater 235 being controlled by the switch 255-25!. If the fuel is burning the stack temperature will rise in a relatively short time to a value at which the stack thermostatic element 245 causes counterclockwise movement of the stack arm 2 toits hot position as shown in Fig.

4. In this position the stack switch including the fixed contact 253 is open, which breaks the enersizing circuit for the igniter relay 245 and thus places the igniter 2l5 out of operation. Due-to the relay coil 242 being deenergized, less current would pass through the thermostat 2 l5 which controls the current to both relay coils. This diminishing of the current through the thermostat would reduce the heating effect of the themestat heater 2i5b. In order to avoid this undesirable result the movable contact of the stack arm engages the iixed contact 254 as shown in Fig. 4, which energizes a ballast resistor 255 as follows: from lockout switch lever 235, wire 25l, wire 255, ballast resistor 255, fixed contact 254, stack arm 24! and wires 215 and 255 to secondary 225. This ballast resistor 255 is sized was to draw the same amount of current as the relay coil 242. Thus by substituting this ballast resistor 255 in the circuit in place of the coil 242 the current passing through the thermostat 215 is maintained constant and thus the heating efl'ect of the anticipating heater 2"!) is maintained constant. The heater 235 will remain energized even after the stack arm 241 reaches it hot position and thus will cause the bimetal element 231 to be slowly heated. After a relatively long period of time it the thermostat 215 still calls for heat this element will move sumciently to disengage both of the latch members 23,4 and 245 as shown in H8. 4. Duetothe stackarm 24lbeinginthe hotposition the lookout switch 235233 will remain closed.

. peraturewill fall to a relatively low value at 225 extends from the lockout switch lever 235,

through wire 251, stationary contact 221a, hi-

which the stack thermostatic element causes movement of the stack arm 24! from the hot positionasshowninFig.4backtothecoldposition shown in Fig. 3. During this movement the actu- I of the latch member I, thus raising this latch member for permitting the bimetal element 231 to return to its com position wherein it supports the latch member 234. This action occurs before the stack arm 2 disengages the latch member 234 and thus insures that the lockout switch will remain closed. The arrangement just described by insuring return of the bimetal element 2 to its cold position before return of the stack arm ill to its cold position insures againsta false lockout as might occur if the stack temperature should fall at a fast rate. In Figs. 1 and zitwillbenotedthatifthestackarmllreturns to its cold position before the bimetal element returns to its cold position a lockout will occur even though the fire may be burning. The arrangement of Fig. 8 avoids any possibility of this happening. Obviously the stack unit I" of Fig. 3 may be substituted for the units of Figs.

1 and 211 desired.

In the event that the fire is out, the stack temperature instead of rising as described above will remain constant and thus the stack arm I will remain in its cold position. Thus the energizing circuit for the relay in will remain closed and also the energizing circuit for the timer heater III vwill remain closed, these circuits being controlled y the switch III of the stack unit ill. After a period or time. such as ten minutes. the heater 228 will cause the bimetal element 22'| to be heated to a point at which it disengages its movable contacts from the fixed contacts 221a and III. This will break the circuit for the motor relay an and thus place the stoker out of operation. This will also break the energizing circuit for the heater 228 which permits the bimetal element 221 to begin cooling. Thus at this time the igniter remains in operation and the stoker is out of operation, which prevents air from the stockerfaniromdissipatingtheheat fromthe igniter. After a period of time, such as ten minutes. the bimetal element 221 cools down sum' ciently to cause reengagement of the contacts thereby energizing relay 2|! and heater 228. Thus the stoker is restarted.- If-ignition occurs the stack temperature will rise causing movement ofthe stack arm :41 to its hot position. 'lhiswlll cause deenergization of the igniter Ill and also cause deenergisation' of the heater III thereby limited to the specific disclosure but may be prac-- ticed in various other forms. Also while the invention includes a complete control system for both attempting rekindling and finally shutting down the system, parts of the complete system may be employed in some instances without others. It is therefore desired to be limited only by the scope of the appended claims.

What is claimed is:

1. In a control system for a stoker having an air feeding portion, a fuel feeding portion and an igniter, the combination of, control mean recontrol means and also normally preventing '09- sponsive to the demand for heat from the stoker for placing the same into and out of operation and automatic means including combustion responsive means for normally rendering the igniter inoperative when combustion is present, while rendering the igniter operative and intermittently rendering at least a portionof the stoker inoperative when combustion is not present.

2. In a control system for a stoker having an air feeding portion. a fuel feeding portion and an igniter, the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation, igniter control means controlled by said control means and including a combustion responsive means,

id igniter control means normally preventing the igniter from operating when the stator is placed out of operation by the first mentioned eration of the igniter when combustion ispres. eat, and means controlled by combustion respon. sive means for intermittently. placing at least one of said portions out of operation while lmltting operation of the igniter when combustion is not Premnt.

3. In a control system for a stoker having an air feeding portion, a fuel feeding portion and an igniter. the combination of. control means responsive to the demand for heat from the stoker for permitting continuous operation of the stoker until the demand for heat issatisfied.

'Ifignitiondoesnotoccurthetimerfltgoes through successive cycles of heating and cooling insuattemptstokindle thefire.thisactlon occurring until the bimetal element ll! of thestackunitthelatchmembertlt.

tained,ahutsdownthesystem. Itwill'alsobeapparent that the present invention provides a novel control system for shutting down the nateminresponsetothefireheingout. While three forms of the invention have been disclosed it will be apparent that the invention is not underthecontrolof the same into and out of operation, a combustion responsive device. means controlled by said combustion responsivedevicc for permitting operation of the igniter when combustion is not present and normall rendering the igniter inoperative when combustion is present, and combustion controlled timing means for rendering at least one of said portions alternately operative and inoperative when combustion is not present. while permitting continuous operation of said one portion when combustion is present.

tlnacontrolsystemforastokahaningan air feeding portion. a fuel feeding portion and an igniter. the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation. said igniter being controlled y said control means and rendered inoperative when the stoker, is placed out of operation by said. control means. and combustion controlled timing means for rendering at least one of said portions inoperative for short'periods of time with the igniter operative when combustion is not present. while permitting continuous operation of said one-portion said control means when combustion is present.

5. In a control system for a stoker having an air feeding portion. a fuel feeding portion and an igniter. the combination of. control means responsive to the demand for heat from the stoker for placing the same into and out of operation. said igniter being controlled by said control means and rendered inoperative when the stoker is placed out of operation by said control'means. timing means for preventing operation of at least one of said portions for certain periods while permitting operation of the igniter, and combustion responsive means for normally preventing said timing means from rendering said one portion inoperative when combustion is present.

6. In a control system for a stoker having an air feeding portion, a fuel feeding portionand an igniter, the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation, said igniter being controlled by said control means and rendered inoperative when the stoker is placed out of operation by said control means, timing means for preventing operation of at least one of said portions for certain periods while permitting operation of the igniter, and combustion responsive means for normally preventing said timing means from rendering said one portion inoperative and for rendering the igniter inoperative when combustion is present.

'7. In a control system for a stoker having an air feeding portion, a fuel feeding portion and an igniter, the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation, said igniter being controlled by'said control means and rendered inoperative when the stoker is placed out of operation by said control means, timing means for preventing operation of at least one of said portions while permitting operation of the igniter, said timing means comprising a thermostatic switching mechanism and a heater therefor, said switching mechanism controlling both said one portion and the heater in a manner to cause said one portion to be intermittently rendered operative and inoperative, and combustion responsive means for rendering said one portion continuously operative under the control of said control means when combustion is present.

8. In a control system for a stoker having an air feeding portion, a fuel feeding portion and an igniter, the combination of, control means responsive to the demand for heat from the stoker for placing the same-into and out of operation, automatic means including combustion responsive means for normally rendering the lgniter inoperative when combustion is present, while rendering the igniter operative and intermittently placing at least one of said portions out of operation when combustion is not present, and means including a switch requiring manual reset for placing said stoker out of operation if said igniter fails to cause combustion.

-9. In a control system for a stoker having an air feeding portion, a fuel feeding portion and an igniter. the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation, said igniter being controlled by said control means and rendered inoperative when the stoker is placed out of operation by said control means, timing means for preventing operation of at least one of said portions for certain periods while permitting operation of the ighiter, combustion responsivev means for preventing said timing means from rendering said one portion inoperative when combustion is present. and means includin a switch requiring manual reset for placing said stoker out of operation if said igniter fails to cause combustion.

10. In a control system for a stoker having an sive means for normally preventing said timing" means from rendering said one portion inoperative when combustion is present, and means including second timing means set for a relatively long timing and a manually resettable lock-out switch for placing the stoker out of operation if the igniter fails to cause combustion.

11. In a control system for a stoker having an air feeding portion, a fuel feeding portion and an igniter, the combination of, control means responsive to the demand for for placing the same into and out of operation,

a lockout switch biased to open position and arranged to prevent operation of the stoker when said switch is open, a time controlled element arranged when in a first position to hold said switch closed and when in a second position to release said switch, a combustion controlled element arranged to hold said switch closed independently of said time controlled element when combustion is present while releasing said switch when combustion is not present, manually resettable latch means for preventing closure of said switch by either of said elements, means controlled by said control means for controlling said time controlled element in a manner causing said element to release said switch a predetermined time after the stoker is placed in operation, timmeans for intermittently preventing operation of at least one of said portions while permitting the igniter to operate, and means actuated with said combustion controlled element for rendering said timing-means inoperative upon presence of combustion.

12. In a control system air feeding portion and a fuel feeding portion, the combination of, control means responsive to air feeding portion, a fuel feeding portion and an the demand for heat from the stoker for placin the same into and out of operation, a lockout switch biased to open position and arranged to prevent operation of the stoker when said switch is open, a time controlled .element arranged when in a first position to hold said switch closed and when in a second position to release said switch, a combustion controlled element arranged to hold said switch cloud independently of said.

time controlled element when combustion is present while releasing said switch when com bustion is not present, manually resettable latch means for preventing closure of said switch by either of said elements, and means controlled by said control means for controlling said time controlled element in a manner causing said element to release said switch a predetermined time after the stoker is placed in operation.

13. In a control system for a burner, the combination of, control means responsive to ,the demand for heat from the burner for placing the same into and out of operation, a lockout switch operation of the burner when the switch is open, a timer including a bimetal element and a heater therefor, said bimetal element when in a first position preventing opening of the lockoutswitch and in a second position permitting the lockout switch to open, a

arranged to prevent heater switch controlling said heater and acbimetal element upon movement tuated by said its second position, latch means thereof toward heat from the stoker for a stoker having an I airfeeding portion, a fuel feeding portion and an igniter, the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation, timing means controlled by said control means and arranged to prevent operation of the igniter when the stoker is first started, while intermittently placing the ignite: into operation and at least one of said portions out of operation after a timed period following starting of the stoker, and combustion responsive means arranged to render the timing means inoperative upon presence of combustion.

15. In a control system for a stoker having an air feeding portion, a fuel feeding portion and an igniter, the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation, timing means including a warp switch having an electric heater for controlling said igniter and one of said portions, said warp switch having an initial position in which the igniter is rendered inoperative and said one portion operative and a second position in which the igniter is rendered operative and said one portion inoperative, means for controlling said electric heater in a manner to cause said warp switch to be in its first'position upon starting of the stoker and to move to its second position thereafter, and then to return to its first position, and combustion responsive means'arranged upon presence of combustion normaiLv to maintain said one portion in operation and prevent operation of the igniter.

16. In a control system for a stoker having an air feeding portion, a fuel feeding portion and an igniter, the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation,. timing means including a warp switch having'an electric heater for controlling said igniter and one of said portions, said warp switch having an initial position in which the igniter is rendered inoperative and'said one portion rendered operative and a second position in which the igniter is rendered operative and said one portioninoperative, means for. controlling said electric heater in a manner to cause said warp switch to be in its first position upon starting of the-stoker, to move to its second position thereafter, and then to return to its first position, and a combustion responsive switch also controlling said heater and actingupon presence of combustion to cause said warp switch to remain in its first position. 1

17. Ina control system for a stoker having an air feeding portion, a fuel feeding portion, and anelectric igniter. the combination of, a high voltage circuit for the ignlter and having a normally open igniter control switch therein, a transformer having a primary and secondary, the primary being connected across said igniter control switch, a relay for controlling the stolrer, a switching device responsive to demand for heat from the stoker, a control circuit for said asaasn relay including said switching device and secondary. electrical time delay means effective when energized a predetermined time to cause closure of said igniter control switch, means actuated upon closure of said igniter control switch for deenergizing said electrical time delay means, and a combustion switch arranged upon presence of combustion to deenergize said electrical time delay means.

18. In a control system for a stoker having an air feeding portion, a fuel feeding portion and an igniter, the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation, timing means controlled. by said control means and arranged to prevent operation of the igniter when the stoker is first started, while intermittently placing the igniter into operation and one of said portions out of operation after a timed period following starting of the stoker, combustion responsive means arranged to render the timing means inoperative upon presence of combustion, and lockout means operative after a number of unsuccessful attempts to cause ignition for placing the stoker out of operation.

19. In a control system for a 'stoker having an airfeeding portion,afuelfeedingportionand an igniter, the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation, control means operative upon starting of the stoker to place the igniter into operation and after a period of time to place one of said portions alternately out of and into operation.

and combustion responsive means arranged upon presence of combustion to cause the igniter to be placed out of operation and said one portion to be maintained in operation.

20. In a control system for a sticker having an] air feeding portion, a fuel feeding portion and.

an igniter, the combination of, control means responsive to the demand for heat from the stoker for placing the same into-and out of operation, control means operative upon starting of the stoker toplace the igniter into operation and after a period of time to place one of said portionsalternately out of and into operation.

- combustion responsive means arranged upon presence of combustion to causethe igniter to be placed out of operation and said one portion to be maintained in operation, and lockout means operative after a number ofunsuccessful attempts to cause ignition for placing the stoker' out of operation.

- 21; In a control system for a stoker having an air feeding portion and a fuel feeding portion. the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation. means responsive to heat from the fire and operative when said control means calls for heat to' intermittently place one of said portions out of and into operation when the fire is apparently out, and means including manually resettable means for placing the stoker out of operation thereafter if combustion does not take place.

22. In a control system for a stoker having an air feeding portion, a fuel feeding portion and an igniter. the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out of operation, igniter control means including combustion responsive means, said igniter control means being constructed and arranged normally to prevent eiIective operation of'the ignite:- when combo,

'at least one air feeding portion,

a,sss,su

tion .is present while causins. operation of the igniter to kindle the fire when combustion is not present, and means for preventing operation of of said stoker portions for a period of time while the igniter operates and ior then placing said one portion into operation.

23. In a control I a fuel ieedlngportion and an electric igniter element, the combination oi. control means responsive to the demand for heat from the stoker for placing the same into and out of operation. and means responsive-to the condition of the lgniter element for preventing operation of at least one of said portions when the igniter elementis inoperative.

24. In a control system for a stoker having an a fuel feeding portion and an electric igniter element. the combination oi. control meansresponsive to the. demand for heat from the stoker for placing the same into and out of operation,-igniter control means for the igniter element for selectively placing the same into or out of operation, and means including a controlling said igniter control system for a stoker having an air feeding portion,

' air feeding portion,

{mm the stoker for extending through the igniter element tor means.

- 25. In a control system tor a stoker having an air feeding portion. a fuel feeding portion and an electric igniter element, the combination of, control means responsive to the demand for heat from the stoker for placing the same into and out oi operation, igniter control means (or the igniter element for selectively placing the same into or out of operation, and means including a circuit circuit extending through the ignlter element for.

controlling said ilrst mentloned'control means.

28. In a control system for a stoker having an a iuel ieeding portion and an electric igniter element, the combination of. control means responsive to the demand for heat placing the same into and out of operation, igniter control means tor the ignite: element ior into or out of operation, and means including a igniter element for controlling both of said control means.

CLIFFO RD HOTCHKISS.

selectively placing the same 

